The capital is braced for mass anti-government protests tomorrow as anarchists pledge to bring chaos to the streets.

Up to 250,000 people are expected to join the TUC anti-cuts march - expected to be the biggest since the Iraq War protest in 2003, when at least 750,000 took to the streets.

But extremists have vowed to hijack the official union action, March for the Alternative, and numbers are expected to be swelled by "feeder" marches by student and anarchist groups. The Evening Standard has been told dozens of groups are planning to start their own demonstrations at 2.11pm.

Militants aim to target banks and shops along Oxford Street with flash mobs, and occupy Hyde Park, Parliament Square and Trafalgar Square before converging on a "secret target" for a "spectacular mass occupation". One of the targets is believed to be the HQ of defence company BAE Systems in Carlton Gardens. About 4,500 police are expected to be deployed in the capital. West End firms have been meeting police to formulate security plans, with shops ready to close if protests spiral out of control.

Stores and businesses have hired extra security and are clearing pre-mises of loose equipment that could be used as weapons. Transport for London is primed to shut Tube stations if numbers grow too rapidly.

CLICK ON THE IMAGE BELOW TO SEE THE FULL IMAGE

Westminster council's cabinet member for business, Brian Connell, said: "The West End is very much open for business this weekend. We will be working with the police to ensure those not involved with the protest remain as unaffected as possible."

Jace Tyrrell, director of communications at the New West End Company, which represents traders, said proprietors were "remarkably calm".

He added: "We have had a number of briefings with the police looking at operational plans, vigilance, etc. They have a huge amount of resources to manage the expected crowds and any splinter protest groups. There is no panic."

One protest organiser, Chris Knight, said the glass-fronted BAE building in Carlton Gardens was "due for demolition". He claimed: "BAE is the worlds largest military contractor and weapons supplier of choice to dictators around the globe, notably the Saudi regime who are currently occupying Bahrain and firing live rounds at peaceful protesters.

"That building is due for demolition - ground floor, lower ground floor and the first floor. It's something that people involved in the anti-war movement have been thinking about for a while." BAE could not be reached for comment.

Knight, who was sacked from his University of East London post over claims he inciting violence at the G20 riots in April 2009, is linked to two protest groups, the Battle of Britain and the Armed Wing of the TUC. He has no links to the official TUC prorest. Other groups set to take action include the Anarchist Federation and Militant Workers Bloc. Resist26, Network X, and UK Uncut have plotted to occupy five key areas as part of a "Pentangle Plan", including Buckingham Palace, Piccadilly and around the Hilton Hotel at Hyde Park. In Oxford Street, demonstrators hope to shut down "tax-dodging" retailers including Vodafone, Boots, and Topshop.